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Re: [Qemu-trivial] [Qemu-devel] [PATCH] tracing.txt: add missing '-' for

From: Eric Blake
Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH] tracing.txt: add missing '-' for trace option
Date: Wed, 13 Jun 2018 06:27:49 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0

On 06/12/2018 10:50 PM, Emilio G. Cota wrote:
On Tue, Jun 12, 2018 at 23:15:49 -0400, Yaowei Bai wrote:
Signed-off-by: Yaowei Bai <address@hidden>
  docs/devel/tracing.txt | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/devel/tracing.txt b/docs/devel/tracing.txt
index 07abbb3..6ab32cc 100644
--- a/docs/devel/tracing.txt
+++ b/docs/devel/tracing.txt
@@ -18,7 +18,7 @@ for debugging, profiling, and observing execution.
3. Run the virtual machine to produce a trace file: - qemu -trace events=/tmp/events ... # your normal QEMU invocation
+    qemu --trace events=/tmp/events ... # your normal QEMU invocation

The second dash is not missing; both '-args' and '--args' work.

'-args' seems to be favoured though; see `qemu -h' or `qemu --h' :-)

Actually, we're trying to fix that:

The one-vs-two dash usage is only supported in qemu, not in qemu-nbd or qemu-img (that is, qemu acts as if it uses getopt_long_only(), while the others use getopt_long() - except that we hand-rolled the parser in qemu, meaning you might find quirks where it sometimes doesn't even match getopt_long_only()).

At any rate, since --trace is an option that is supported across multiple binaries, we SHOULD favor the double-dash spelling in our documentation, so that you can consistently reuse the same --trace invocation without worrying whether the binary parses its arguments with getopt_long() (where double is required) or like getopt_long_only() (where the double is optional but supported).

So I'm in favor of this patch, although it may need more of a commit message summarizing the justification I've just pointed you to.

Reviewed-by: Eric Blake <address@hidden>

Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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